60 A-frame timbered bunkers built into the sides of bomb craters, each with an average overhead cover 10-feet-thick, the system was connected to a large command bunker by a network of interconnecting tunnels. The command bunker featured an aperture overlooking Con Thien and C-2 and documents found in the bunker indicated that the PAVN had been observing and reporting the movement of helicopters, tanks, and trucks entering and leaving Con Thien and C-2. Early August saw little contact with the PAVN other than an encounter by Company F, 9th Marines with 30 PAVN, 3 km east of Con Thien. In the face of artillery and fixed-wing support, the PAVN broke contact and the Marines began a sweep through the area during which they regained contact. The PAVN again broke and ran, and Company F moved through the area, capturing a number of weapons and counting 11 PAVN dead. On 15 August, a PAVN company attacked a four-man Marine reconnaissance team southeast of Con Thien near the abandoned airstrip at Nam Dong. The patrol returned fire and requested reinforcement, while simultaneously calling in preplanned artillery fires. Within minutes a platoon from Company A, 1st Marines, accompanied by three M48 tanks, moved out of positions 1 km away and headed south to assist. The coordinated attack, which included more than 150 rounds of 105mm artillery, 40 rounds of 4.2-inch mortar, 75 rounds from the 90mm guns of the tanks, and airstrikes by Marine UH-1E gunships accounted for several NVA dead. As PAVN activity continued to increase in the eastern DMZ, particularly north of Con Thien, the Marines decided to act. In addition to sightings of enemy tanks, Marine fighter pilots and aerial observers reported spotting trucks, truck parks, camouflaged revetments, storage bunkers, and trenchlines. Of special interest were repeated sightings of low, slow moving lights during hours of darkness which, it was assumed, came from enemy helicopters thought to be resupplying forward positions with high priority cargo such as ammunition and medical supplies or conducting medevacs. On 19 August, after 60 Arclight strikes 2nd Battalion 1st Marines (2/1) assaulted into three LZs in the Trung Son region of the southern DMZ, 5 km north of Con Thien. Supported by a platoon of tanks from 3rd Tank Battalion, 2/1 swept the area but found no evidence of use by VPAF helicopters. During the extraction one CH-46 Sea Knight was destroyed by a command